This invention relates to a technology for backing up data stored in a network attached storage (NAS), and more particularly, to a technology for backing up data stored in a NAS which is not locally coupled to a backup device.
In order to back up data stored in a network attached storage (NAS), there are two types of backup: network backup and local backup.
In the network backup, a NAS stores backup data in a backup device coupled to the NAS via a LAN (Local Area Network). That is, in the network backup, since the NAS and the backup device are coupled with each other via the LAN, multiple NAS's can share a single backup device.
On the other hand, in the local backup, a NAS stores backup data in a backup device locally coupled to the NAS. That is, in the local backup, the NAS and the backup device are locally coupled with each other. Consequently, in the local backup, the backup can be carried out without influence of the traffic of a LAN.
A description will now be given of backup for a computer system where a NAS, which is not locally coupled to a backup device, and a NAS, which is locally coupled to the backup device, are coupled via a LAN.
The NAS, which is not locally coupled to the backup device, carries out backup by transmitting backup data via the LAN to the NAS, which is locally coupled to the backup device. In this case, a large amount of backup data is transported via the LAN. As a result, the backup data places a burden on communication between a client computer and the NAS.
JP 2004-151824 A discloses a technology to solve this problem. According to this technology, when the traffic on a LAN is low, a NAS, which is not locally coupled to a backup device, transmits backup data to a NAS, which is locally coupled to the backup device. That is, if the traffic on the LAN is high, the NAS, which is not locally coupled to the backup device, suspends the transmission of the backup data.
JP 2005-533314 A discloses a data backup technology for a case where a client computer and a tape device are coupled with each other via an FC (Fibre Channel).